This invention relates to valves for metered aerosol valve chambers and pump chambers in general and more paticularly to an improved construction in such valves permitting a better seal between the valve stem and chamber.
One problem existing in prior art aerosol valves relates to the sealing at the bottom of the metering chamber. Typical of such sealing is that disclosed in my prior U.S. Pat. No. 3,464,596. As disclosed therein, the bottom of the valve stem is ribbed so that when the valve is in the upward, nondispensing position, flow channels from the aerosol container to the metering chamber are established, allowing the metering chamber to fill with the material to be dispensed. Although this arragement works quite well, it has a number of disadvantages. First, because of the ribbed construction at the base of the stem, it is difficult to mold the portion directly thereabove, which portion forms a plastic valve seal, to close tolerances. The result of the ribbed construction is that distortions occur in this area. In order to maintain a good seal, it is then necessary to have a tighter fit than would ordinarily be necessary. Because of this, the spring used for returning the valve stem to its non-dispensing position must be relatively strong. To obtain the required spring force, the spring may be required to virtually fill the metering chamber including that part directly above the plastic seal. Since the spring cannot be reliably constructed to be free of burrs at its end, such burrs may be present and can result in scoring on the sealing portion of the stem. This scoring of the stem along with the distortion resulting from the ribbed construction results in the possibility of inconsistent shut-off and wear at the seal when the stem is depressed, causing loss of vapor or spitting of the product.
Pumps such as that disclosed in my previous U.S. Pat. No. 3,211,346 use the same type of valve to close the pump chamber and can exhibit the same problems.
Thus, it is clear that there is a need in a valve of this nature for an improved type of seal at the inlet to a metering or pump chamber.